The present invention relates to a circuit and, more particularly, to an organic light-emitting diode (OLED) pixel compensation diode.
Organic light-emitting diodes are essential new element for flat panel display devices and have wide applications due to the advantages of self-illumination, high contrast ratio, wide color gamut as well as simple production technology, low cost, low power consumption, and ease of fulfilling flexible display.
Despite the above advantages, OLED display devices incur many problems during applications. For example, in a thin film transistor (TFT) using an OLED as a switch or a driving element, the stability of the gate voltage is critical, particularly in the black state. If the gate voltage is unstable, the brightness of the black state is affected and results in a reduction in the contrast ratio and an increase in the value of the storage capacitor. Thus, the space occupied by the storage capacitor is increased, the output space is reduced, and the pixels per inch (PPI) of the OLED display device is reduced, reducing the performance of the product.
FIG. 1 shows a diagrammatic circuit diagram of a conventional OLED pixel compensation circuit, in which T2 is a driving transistor for driving the OLED to emit light, Cst is a storage capacitor, Dm is a data signal line, En is a control signal line, Sn, Sn−1, and Sn′ are scan signal lines, ELVDD is a power providing the driving transistor T2 with a voltage for driving the OLED to emit light, ELVSS is a cathode voltage, and Vin is an initialization power providing an initialization voltage to the OLED and the gate (node N9) of the driving transistor T2, with the voltage of Vin being smaller than the voltage of the ELVDD and the data voltage. The electrical leakage of the dual gate structures T5 and T6 of the circuit flows from the gate (node N9) of the driving transistor T2 to a voltage node with a more negative voltage. Specifically, the electrical leakage of the T5 dual gate structure flows from the gate (N9 node) of the driving transistor T2 to the ELVSS (as indicated by arrow a), and the electrical leakage of the T6 dual gate structure flows from the gate (N9 node) of the driving transistor T2 to the Vin (as indicated by arrow b). Thus, the gate voltage of the driving transistor T2 will become unstable due to a voltage change resulting from electrical leakage of the T5 and T6 dual gate structures, adversely affecting the performance of the OLED display device.